In this section we look at how to find the input and output of function machines.
Function machines take a number as INPUT and give another number as OUTPUT.
INPUT 

OUTPUT 



Now look at the double function machine below:
This time, we need to multiply the input by 2 and then subtract 1. This gives an output of 9.
5
× 2
 1
?
Practice Questions
Work out the output from these two function machines, then click
to see whether you are correct.
 

Look at the function machine below:
To work out the input, we need to take the output and divide by 4 (the opposite of multiplying by 4).
?
× 4
8
This gives an input of 2.
Now look at the double function machine below:
This time, we need to do the inverse operations from right to left. We divide the output by 3 and then add 5.
?
 5
× 3
6
This gives an input of 7.
Inverse Operations
The table below shows the inverse (i.e. opposite) operations.
Practice Questions
Work out the input to these two function machines, then click
to see whether you are correct.

 


